The present disclosure relates to a recording medium feeding unit including a recording medium loading plate on which a sheet-like recording medium is loaded and positioning members that position the recording medium in the widthwise direction, and an image forming apparatus including the same.
Recording medium feeding units such as a stack tray (also designated as a manual feed tray) and a paper feed cassette are widely used. A recording medium feeding unit holds a pile of a plurality of sheet-like paper (recording media) for separating and feeding the paper one by one to an image forming section provided in the main body of an image forming apparatus in accordance with an image forming operation.
The configuration of a general stack tray will be described. FIGS. 7 to 9 are perspective views illustrating an example of a general stack tray. As illustrated in FIG. 7, the general stack tray 135 includes a paper loading plate 150, a pair of widthwise positioning members 151, a main body 152, a pair of racks 153 (see FIG. 8) and a pinion 154 (see FIG. 8).
Paper is loaded on the paper loading plate 150. The main body 152 holds the paper loading plate 150. The pair of widthwise positioning members 151 position the paper in the widthwise direction perpendicular to a paper feeding direction. Each of the pair of racks 153 extends along the widthwise direction perpendicular to the paper feeding direction (that is, a paper conveyance direction or a direction illustrated with an arrow A). The pair of racks 153 are configured to move in the widthwise direction integrally with the widthwise positioning members 151. The pinion 154 is engaged with the pair of racks 153. The pinion 154 has, on its outer circumferential surface, a pinion gear (not shown) engaged with a rack gear 153a of each rack 153. Accordingly, the pinion 154 is rotated in association with the movement of the racks 153. As a result, when one of the widthwise positioning members 151 is moved, the pinion 154 is rotated, so as to move the other of the widthwise positioning members 151 in the opposite direction to the former widthwise positioning member 151 by the same distance.
If the pinion 154 has such a small rotation load that the widthwise positioning members 151 can be easily moved in the widthwise direction, paper is skewed (inclined) in feeding. In particular, the skew is easily caused in feeding thick paper. Therefore, in order to cope with the feed of thick paper, the rotation load of the pinion 154 is set to be large, in the stack tray 135, for restraining the movement of the widthwise positioning members 151.
Specifically, as illustrated in FIG. 9, a boss 150a serving as the rotating shaft of the pinion 154 is formed on the rear surface of the paper loading plate 150. The boss 150a is provided with a rib 150b for increasing a contact area with the pinion 154. As a result, the rotation load of the pinion 154 is increased so as to restrain the movement of the widthwise positioning members 151.
Incidentally, in some paper feeding device, a paper loading section (corresponding to a paper loading plate) is elevated to secure a side fence (corresponding to the widthwise positioning member).